1# SPDX-License-Identifier: GPL-2.0-only 2 3config HAVE_ARCH_KCSAN 4 bool 5 6config HAVE_KCSAN_COMPILER 7 def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=thread -mllvm -tsan-distinguish-volatile=1)) || \ 8 (CC_IS_GCC && $(cc-option,-fsanitize=thread --param tsan-distinguish-volatile=1)) 9 help 10 For the list of compilers that support KCSAN, please see 11 <file:Documentation/dev-tools/kcsan.rst>. 12 13config KCSAN_KCOV_BROKEN 14 def_bool KCOV && CC_HAS_SANCOV_TRACE_PC 15 depends on CC_IS_CLANG 16 depends on !$(cc-option,-Werror=unused-command-line-argument -fsanitize=thread -fsanitize-coverage=trace-pc) 17 help 18 Some versions of clang support either KCSAN and KCOV but not the 19 combination of the two. 20 See https://bugs.llvm.org/show_bug.cgi?id=45831 for the status 21 in newer releases. 22 23menuconfig KCSAN 24 bool "KCSAN: dynamic data race detector" 25 depends on HAVE_ARCH_KCSAN && HAVE_KCSAN_COMPILER 26 depends on DEBUG_KERNEL && !KASAN 27 depends on !KCSAN_KCOV_BROKEN 28 select STACKTRACE 29 help 30 The Kernel Concurrency Sanitizer (KCSAN) is a dynamic 31 data-race detector that relies on compile-time instrumentation. 32 KCSAN uses a watchpoint-based sampling approach to detect races. 33 34 While KCSAN's primary purpose is to detect data races, it 35 also provides assertions to check data access constraints. 36 These assertions can expose bugs that do not manifest as 37 data races. 38 39 See <file:Documentation/dev-tools/kcsan.rst> for more details. 40 41if KCSAN 42 43# Compiler capabilities that should not fail the test if they are unavailable. 44config CC_HAS_TSAN_COMPOUND_READ_BEFORE_WRITE 45 def_bool (CC_IS_CLANG && $(cc-option,-fsanitize=thread -mllvm -tsan-compound-read-before-write=1)) || \ 46 (CC_IS_GCC && $(cc-option,-fsanitize=thread --param tsan-compound-read-before-write=1)) 47 48config KCSAN_VERBOSE 49 bool "Show verbose reports with more information about system state" 50 depends on PROVE_LOCKING 51 help 52 If enabled, reports show more information about the system state that 53 may help better analyze and debug races. This includes held locks and 54 IRQ trace events. 55 56 While this option should generally be benign, we call into more 57 external functions on report generation; if a race report is 58 generated from any one of them, system stability may suffer due to 59 deadlocks or recursion. If in doubt, say N. 60 61config KCSAN_DEBUG 62 bool "Debugging of KCSAN internals" 63 64config KCSAN_SELFTEST 65 bool "Perform short selftests on boot" 66 default y 67 help 68 Run KCSAN selftests on boot. On test failure, causes the kernel to 69 panic. Recommended to be enabled, ensuring critical functionality 70 works as intended. 71 72config KCSAN_KUNIT_TEST 73 tristate "KCSAN test for integrated runtime behaviour" if !KUNIT_ALL_TESTS 74 default KUNIT_ALL_TESTS 75 depends on TRACEPOINTS && KUNIT 76 select TORTURE_TEST 77 help 78 KCSAN test focusing on behaviour of the integrated runtime. Tests 79 various race scenarios, and verifies the reports generated to 80 console. Makes use of KUnit for test organization, and the Torture 81 framework for test thread control. 82 83 Each test case may run at least up to KCSAN_REPORT_ONCE_IN_MS 84 milliseconds. Test run duration may be optimized by building the 85 kernel and KCSAN test with KCSAN_REPORT_ONCE_IN_MS set to a lower 86 than default value. 87 88 Say Y here if you want the test to be built into the kernel and run 89 during boot; say M if you want the test to build as a module; say N 90 if you are unsure. 91 92config KCSAN_EARLY_ENABLE 93 bool "Early enable during boot" 94 default y 95 help 96 If KCSAN should be enabled globally as soon as possible. KCSAN can 97 later be enabled/disabled via debugfs. 98 99config KCSAN_NUM_WATCHPOINTS 100 int "Number of available watchpoints" 101 default 64 102 help 103 Total number of available watchpoints. An address range maps into a 104 specific watchpoint slot as specified in kernel/kcsan/encoding.h. 105 Although larger number of watchpoints may not be usable due to 106 limited number of CPUs, a larger value helps to improve performance 107 due to reducing cache-line contention. The chosen default is a 108 conservative value; we should almost never observe "no_capacity" 109 events (see /sys/kernel/debug/kcsan). 110 111config KCSAN_UDELAY_TASK 112 int "Delay in microseconds (for tasks)" 113 default 80 114 help 115 For tasks, the microsecond delay after setting up a watchpoint. 116 117config KCSAN_UDELAY_INTERRUPT 118 int "Delay in microseconds (for interrupts)" 119 default 20 120 help 121 For interrupts, the microsecond delay after setting up a watchpoint. 122 Interrupts have tighter latency requirements, and their delay should 123 be lower than for tasks. 124 125config KCSAN_DELAY_RANDOMIZE 126 bool "Randomize above delays" 127 default y 128 help 129 If delays should be randomized, where the maximum is KCSAN_UDELAY_*. 130 If false, the chosen delays are always the KCSAN_UDELAY_* values 131 as defined above. 132 133config KCSAN_SKIP_WATCH 134 int "Skip instructions before setting up watchpoint" 135 default 4000 136 help 137 The number of per-CPU memory operations to skip, before another 138 watchpoint is set up, i.e. one in KCSAN_WATCH_SKIP per-CPU 139 memory operations are used to set up a watchpoint. A smaller value 140 results in more aggressive race detection, whereas a larger value 141 improves system performance at the cost of missing some races. 142 143config KCSAN_SKIP_WATCH_RANDOMIZE 144 bool "Randomize watchpoint instruction skip count" 145 default y 146 help 147 If instruction skip count should be randomized, where the maximum is 148 KCSAN_WATCH_SKIP. If false, the chosen value is always 149 KCSAN_WATCH_SKIP. 150 151config KCSAN_INTERRUPT_WATCHER 152 bool "Interruptible watchers" 153 help 154 If enabled, a task that set up a watchpoint may be interrupted while 155 delayed. This option will allow KCSAN to detect races between 156 interrupted tasks and other threads of execution on the same CPU. 157 158 Currently disabled by default, because not all safe per-CPU access 159 primitives and patterns may be accounted for, and therefore could 160 result in false positives. 161 162config KCSAN_REPORT_ONCE_IN_MS 163 int "Duration in milliseconds, in which any given race is only reported once" 164 default 3000 165 help 166 Any given race is only reported once in the defined time window. 167 Different races may still generate reports within a duration that is 168 smaller than the duration defined here. This allows rate limiting 169 reporting to avoid flooding the console with reports. Setting this 170 to 0 disables rate limiting. 171 172# The main purpose of the below options is to control reported data races (e.g. 173# in fuzzer configs), and are not expected to be switched frequently by other 174# users. We could turn some of them into boot parameters, but given they should 175# not be switched normally, let's keep them here to simplify configuration. 176# 177# The defaults below are chosen to be very conservative, and may miss certain 178# bugs. 179 180config KCSAN_REPORT_RACE_UNKNOWN_ORIGIN 181 bool "Report races of unknown origin" 182 default y 183 help 184 If KCSAN should report races where only one access is known, and the 185 conflicting access is of unknown origin. This type of race is 186 reported if it was only possible to infer a race due to a data value 187 change while an access is being delayed on a watchpoint. 188 189config KCSAN_REPORT_VALUE_CHANGE_ONLY 190 bool "Only report races where watcher observed a data value change" 191 default y 192 help 193 If enabled and a conflicting write is observed via a watchpoint, but 194 the data value of the memory location was observed to remain 195 unchanged, do not report the data race. 196 197config KCSAN_ASSUME_PLAIN_WRITES_ATOMIC 198 bool "Assume that plain aligned writes up to word size are atomic" 199 default y 200 help 201 Assume that plain aligned writes up to word size are atomic by 202 default, and also not subject to other unsafe compiler optimizations 203 resulting in data races. This will cause KCSAN to not report data 204 races due to conflicts where the only plain accesses are aligned 205 writes up to word size: conflicts between marked reads and plain 206 aligned writes up to word size will not be reported as data races; 207 notice that data races between two conflicting plain aligned writes 208 will also not be reported. 209 210config KCSAN_IGNORE_ATOMICS 211 bool "Do not instrument marked atomic accesses" 212 help 213 Never instrument marked atomic accesses. This option can be used for 214 additional filtering. Conflicting marked atomic reads and plain 215 writes will never be reported as a data race, however, will cause 216 plain reads and marked writes to result in "unknown origin" reports. 217 If combined with CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN=n, data 218 races where at least one access is marked atomic will never be 219 reported. 220 221 Similar to KCSAN_ASSUME_PLAIN_WRITES_ATOMIC, but including unaligned 222 accesses, conflicting marked atomic reads and plain writes will not 223 be reported as data races; however, unlike that option, data races 224 due to two conflicting plain writes will be reported (aligned and 225 unaligned, if CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=n). 226 227endif # KCSAN 228